examples-3.x-dev/modules/plugin_type_example/plugin_type_example.routing.yml

# This defines our example page's path to the routing system.
plugin_type_example.description:
  path: '/examples/plugin-type-example'
  defaults:
    _controller: '\Drupal\plugin_type_example\Controller\PluginTypeExampleController::description'
    _title: 'Plugin Type Example'
  requirements:
    _permission: 'access content'